I would say that the gulf between Communism and Fascism was actually a lot smaller than that between Social Democracy and Fascism. Make of that what you will.
Still stealing arguments from Hannah Arendt, I see
The woman who hung out with Heidegger?
Poor Hannah, still only 'Heidegger's girlfriend'. And then you're wondering who's keeping the sisters down?
Though, yes, your point isn't one that's restricted to Arendt's work. I see it all the time. A marxist ( a term that's preferrable to the vagueness of 'communism', which could easily apply to Gracchus Babeuf or someone as well), of course, would argue that it fascism is, in fact, a logical extension of liberalism.